Patent Literature 1: JP 2012-063524 A
Patent Literature 2: JP-2008-501956 A (WO 2005421707 A2)
Patent Literature 1 describes a head-up display (HUD), which projects light on a windshield or combiner in a vehicle and displays a variety of pictures to permit a driver to view them through a windshield. Further, Patent Literature 2 uses a HUD, which displays a guidance picture at a position corresponding to a road ahead of the vehicle as a virtual image that indicates the heading direction (route guide information) indicated by a route guidance of a navigation system.
A conventional technology displays a guidance picture that appears in the scenery in a forward direction of a vehicle as extending from a sky into a road in the heading direction of the vehicle. For example, a displayed picture may overlap with a light portion of a traffic signal that is at a position over a road in the heading direction of the vehicle. Such a case may not permit the driver to promptly recognize the state of the traffic signal.
In addition, a conventional technology displays a guidance picture at a time corresponding to a route guidance of a navigation system. In some cases, a displayed picture may appear to be viewed in close proximity to road signs or road information boards as well as traffic signals in the vehicle forward direction. Such a case may decrease the visibility of the displayed picture or cause the information necessary for driving to be difficult for understanding.